Craniometric Patterns of Three Nigerian Ethnic Groups

Full Length Research Paper

Craniometric patterns of three Nigerian ethnic groups

Odokuma, E. I.1*, Igbigbi, P. S.1, Akpuaka, F. C.2 Esigbenu, U. B.1

1Department of Anatomy, Delta State University, Abraka Nigeria. 2Department of Anatomy, Abia State University Uturu, Abia State, Nigeria.

Accepted 1 February, 2010

The usefulness of craniometry in facilitating proper identification of skeletal remains and in emphasizing a common origin of studied populations is far reaching. Conducting anthropological studies with the aim of obtaining the characteristics of ethnic groups assists not only in understanding the frequency distribution of human morphologies but also in providing the basis for comparison of races. Craniometric patterns were studied in three selected ethnic groups in Nigeria and this study will no doubt form a baseline data for subsequent studies especially as regards the studied populations. This study involved 699 (male 361; female 338) volunteers whose age ranged 18 and over. Respondents were selected along three ethnic groups including Urhobo (male 156; female 147), Ibo (male 141 female 145) and Edo (male 64; female 46) and it was ensured that population for the study was collected using a random stratified method. The cranial volume was measured using standard techniques and it was shown to exhibit strong sexual dimorphism and was useful in differentiating inter and intra population groups. The results showed a significant effect of cranial volume on the measured ethnic groups at 0.05 level of significance. While the Ibo’s had an average cranial volume of 1273.39 cm3, that of the Urhobo’s was 1255.89 and 1310.08 cm3 for the Edo people. Also the cranial capacity of male (1334.34 cm3) was significantly different from that of female (1204.54 cm3) in all the studied tribes, male being larger than that of female p < 0.05.

Key words: Craniometric patterns, ethnic groups, head length, head breadth, auricular height.

INTRODUCTION

Knowledge of the cranium of either a dry skull or of a capacity (Douglas, 1990). living being is of significant importance to the study and Measuring of man’s potential intellectual capacity from comparison of populations with various fundamental sources other than direct observations and testing is differences like racial, geographic, ethnic and dietary derived from direct, indirect and inferential data. The characteristics. Cranial volume expresses several aspects direct data is obtained from measuring cranial capacity of growth and development and permits critical evaluation and examining casts which ‘expose’ the interior of the of unusually large, small or misshapen crania (Haack and skull. The indirect evidence comes from the study of com- Neihoff, 1971). parative brain sizes, which is based on the assumption Craniometric data is used in mainstream science to that there is a correlation between brain size and configu- analyze the evolution of the human species in archeo- ration and behavioral studies. Other indirect evidence logy. Since man’s brain is relatively larger than other comes from the study of fossil remains of non-cranial animals, it is natural for man to conclude that the brain is parts which infer manual dexterity and visual acuity the hallmark of man and the measurement of it must be (Douglas, 1990). Very little relationship between cranial the key to the understanding of his unique intellectual capacity and human intelligence has been shown owing to marked variability in man’s cranial capacity. Several craniometric studies involving Caucasian, Mongoloid and Americans have been conducted. Attempts at explaining *Corresponding author. E-mail: [email protected]. homogeneity of African populations have led to a number Tel: 2348035658134. of studies. Howells, (1989); Froment, (1992a) and Lahr,

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Table 1. Means, standard deviation, sum and range of cranial capacities of the three populations.

Cranial capacity N Mean Std. dev. Sum Minimum Maximum Urhobos 303 1256.00 144.65 380535 805.79 1646.00 Ibos 286 1273.00 134.98 364189 926.01 1653.00 Edos 110 1310.00 128.75 14410 1013.00 1611.00 Total 699 1272.00 139.36 888833.00 805.79 1653.00

Table 2. Mean cranial capacity (CC) of the three cultures.

R-Square Coefficient of variation Root mean square CC Mean 0.41 9.37 119.23 1271.58

(1996) suggested that despite the general opinion that Cranial volume (cv) = (0.000400(L-11) (B-11) (HT-11) + 206.60---- Africans did appear to be homogenous in certain morpho- females logical characteristics, observed polymorphisms where (Lee and Pearson, 1901). far from homogenous. In another study, Hiernaux (1976) The following parameters were obtained: maximum head length (L) explained that the variations of craniometric charac- (Glabellar to inion length) in (cm), maximum head breadth (B) teristics were distinctly different from the previous racial (distance between the two parietal eminences) in (cm), auricular categorizations of Africans (Leaky, 1935; Coon, 1971). height (HT) (External acoustic meatus to the highest point of the Through skull morphology, population differentiation has vertex) in (cm) and cranial capacity (cc).The means obtained from the above variables were then subjected to analyses of variance been explored previously by three main recent studies (ANOVA) for comparison within cultures. Finally, multivariate (Hiernaux 1976; Howells 1989; Froment, 1992; 1998), analyses (MANOVA), between the studied cultures were made for showing that not only vault features but also various assessment of statistical significance and interactions. facial characteristics are responsible for both inter and intra-regional differences within sub-Saharan Africa. Hiernaux (1966, 1968, 1974, 1976) highlighted on inter- RESULTS and intra-population variability in sub-Saharan Africa. The present study investigate craniometric patterns in Mean cranial volume was 1271.58 ± 139.36 cm3 with three selected ethnic groups in Nigeria and this study will minimum values of 805.79 cm3 and maximum values of no doubt form a baseline data for subsequent studies 1653.00 cm3 (Tables 1 and 2). Tribe had a significant especially as regards the studied populations. As far as effect on cranial capacity at 0.05 levels of significance we know, very scant study, if any, on cranial capacity has (Table 3). Gender was also observed to have a significant been conducted in the studied populations. effect on cranial capacity at 0.001 level of significance (Tables 3, 4, 5 and 6). Mean separation showed that the cranial capacity of Ibo and Urhobo tribes were similar and MATERIALS AND METHODS were both significantly different from the Edo people

(Table 6). The population sample for this study included 699 (male 361; female 338) volunteers whose age ranged between 18 and 33 The mean cranial capacity of the Edo’s was 1310.00 ± 3 3 years since little or no morphological change was expected in the 128.76 cm . The range was from 1013.00 to 1611.00 cm skulls of such individuals normally.. Data was obtained from persons and there was significant difference between female and whose parents and grand parents were of Nigerian origin and male values (Tables 4 and 5). showed no obvious physical cranial defect. Data from closely The mean cranial capacity for Ibo’s was 1273 ± 134.98 related individuals were excluded to avoid familiar peculiarities that cm3 with maximum of 1653 cm3 and minimum value of may occur with such measurements. Respondents were selected 3 along three culture lines of Urhobo (male; female), Ibo (male; 926.01 cm (Table 1) .There was a significant effect of female) and Edo (male; female) speaking people and it was ensured gender on cranial capacity (p < 0.001) as shown in Table that population for the study was collected using a random stratified 3 .The mean male cranial capacity was 1323 cm3 (Table method (Andy, 1992). Sample size for studies of this nature was 4) while the mean female value was 1184.63 cm3 (Table determined using a standard formula (Andy, 1992). 5). Cranial volume (cv) = (0.00037(L-11) (B-11) (HT-11) + 406.01----- The mean cranial capacity for the Urhobo’s was 3 males 1255.89 ± 144.65 cm (Table 1). The minimum cranial

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Table 3. Effect of tribe, age and gender on cranial capacity.

Source DF Type III sum of Mean F Value Pr > F squares square Tribe 2 109410.48 54705.24 3.85 0.02 Age 48 833339.10 17361.23 1.22 0.15 Gender 1 563016.68 563016.68 39.61 <.0001

Table 4. Cranial capacity for male for the three populations.

Tribe Mean Standard deviation Maximum Minimum Edo 1351.07 103.05 1611.09 1200.49 Ibo 1339.30 99.00 1652.87 1119.01 Urhobo 1334.34 152.48 1645.82 1082.37 Average 1310.65 124.57 1695.20 983.98

Table 5. Cranial capacity of female of the three populations.

Tribe Mean Standard deviation Maximum Minimum Edo 1253.04 139.91 1524.88 1013.47 Ibo 1209.29 134.68 1630.42 926.01 Urhobo 1204.54 142.21 1588.62 805.79 Total 1208.77 138.65 1630.42 815.05

Table 6. Variation in gender cranial capacities for the three tribes.

Grouping Mean N Tribe A 1310.08 110 Edo B 1273.39 286 Ibo B 1255.89 303 Urhobo

Means with the same letter are not significantly different.

capacity was 805.79 cm3 and maximum cranial capacity, (1996). While the Ibo’s had an average cranial capacity of 1646 cm3 (Table 1). 1273.39 cm3, that of the Urhobo’s was 1255.89 cm3. The Edo’s was 1310.08 cm3. This may be attributable to a common ancestral origin of the Ibo and Urhobo people or DISCUSSION inter marriages which are very common between these cultures with interchange of physical characteristics over The findings in this study are similar to previous studies the years since these people have been cordial neigh- (Morton, 1839) where the mean cranial volume of the bours. Also the cranial volume of male (1334.34 cm3) was skulls of whites was 1,425 cm³, while that of the Blacks significantly different from that of female (1204.54 cm3) in was 1,278 cm³. Based on the measurement of 144 skulls all the studied tribes, male being larger than that of of Native Americans, Morton (1839) reported a figure of female p < 0.05. This important characteristic which was 1,344 cm³. Gould (1981) and Rushton (1995) have also also previously observed (Rushton, 1995) is very important showed very similar figures. Tribe had a significant effect in sex determination. Cranial volume has demonstrated on cranial volume at 0.05 levels of significance. Inter- strong sexual dimorphic patterns and thus individuals cultural comparisons demonstrated significant variation from the studied populations can be differentiated from as reported by Howells (1989), Froment (1992) and Lahr those of other races and perhaps African groups.

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Conclusion Froment A (1992). Origines du peuplement de l’Égypte ancienne : l’apport de l’anthropobiologie, Archéo-Nil. 2 : 79-98. Froment A (1998). Le peuplement de l’Afrique Centrale: contribution de The craniometric patterns of three indigenous Nigerian la paléoanthropologie. In Delneuf M, Essomba JM & Froment, A.25 ethnic groups have been presented highlighting certain (eds) Paléoanthropologie en Afrique centrale: Un Bilan de features common to Nigerians and perhaps indeed West l’Archéologie au Cameroun: 13-90. Paris: L’Harmattan. African populations. It has also been shown that cranio- Haack DC, Meihoff EC (1971). A method for estimation of cranial capacity from cephalometric Roentgnograms. Am. J. Phys. metric patterns are significant indices for inter ethnic Anthropol. 34: 447-452. differentiation of population groups. In spite of these Howells WW (1989). Skull shapes and the map: craniometric analyses observations, similarities which enabled intracultural diffe- in the dispersion of modern homo. Papers of the Peabody Museum of rentiation did occur as exhibited by craniometric patterns Archaeology and Ethnology 79. Cambridge, MA: Peabody Museum. Lahr MM (1996). The Evolution of Modern Human Diversity, a Study of in this study. Inevitably therefore, craniometric studies are Cranial Variation. Cambridge: Cambridge University Press. most essential in the study of population dynamics espe- Lee A, Pearson K (1901). Data for the problem of evolution in man: VI. cially with respect to quantitative variables. This study A first study of the correlation of the human skull. Philos. Trans. R. has further demonstrated the well established genealogy Soc. London, 196: 225-264. Morton SG (1839). Crania Americana; An Inquiry into the Distinctive that the three studied populations may have evolved from Characteristics of the Aboriginal Race of America Cambridge a common ancestral origin. Encyclopedia Vol. 65. Rushton JP (1995). Race, evolution and behaviour: A life history perspective. New Brunswick, NJ: Transaction.

REFERENCES

Andy IJ (1992). Fundamental statistics for Education and Behavioral Sciences Kraft Books Limited, Oyo State, Nigeria. Douglas SJ (1990). Cranial capacity and endocranial cast. T. J. 4(1): 56-65. Gould SJ (1981). American Polygeny and craniometry before Darwin: blacks and Indians as separate, inferior species. In: Harding, Racial Econ. Sci. 84-115. Froment A (1992a). La différenciation morphologique de l’homme moderne: congruence entre forme du crâne et répartition géographique du peuplement, Comptes Rendus de l’Académie des Sciences (Paris), série III, 315: 323-329.